There are many electrical devices used about the ordinary household which are subject to electrical shock hazards whenever the user of the device comes in contact with an electrical ground, as for example touching a water hydrant, accidentally submerging the device in water, or worse yet, providing circuitry through one's body due to malfunction of the insulation somewhere in the device.
Domestic appliances are connected to a supply of alternating current which flows 60 cycles per second and accordingly each 120th of a second delivers up to 120 volts of electrical shock to any person who may inadvertently come in contact with this power source. It is therefore logical that some sort of sensor device could be made to sense the malfunction during the first cycle of current flow and utilize the sensed condition for immediately disconnecting the device from the power souce. It is possible to make the response rate of such a device fast enough to preclude a person from realizing that he has received an electrical shock.
Such a safety apparatus should be simple in design so as to be economically feasible for use in conjunction with inexpensive domestic appliances in order for the manufacture to maintain competitive prices. Accordingly, the present invention relates to an electrical device whose purpose is to prevent electrical shock hazards, especially in conjunction with small appliances. This invention is an active device which constantly monitors specific conditions which may be used to activate the device to remove the power source from a load, such as a domestic appliance, and thereby prevent electrical shock hazards and other physical electrical dangers such as fire. The method and apparatus of this invention differ from other types of electrical protection devices, such as fuses and circuit breakers, in several ways, as for example:
1. The device has a typical activation time of 50-300 microseconds;
2. The device activates on conditions other than short-circuits;
3. The device can be located in the appliance; and,
4. The device can be made to activate in response to either current or voltage sensing.